Inside Health

Personal Health

By Jane E. Brody

Published: June 9, 1993

MANY factors can touch off an asthmatic attack in people prone to this frightening constriction of the airways: pollens, dust, cigarette smoke and even cold air. But one of the most distressing and most often unrecognized triggers is vigorous physical exercise.

Exercise-induced asthma is extremely common, affecting more than 80 percent of people with ordinary asthma, 30 to 40 percent of those with allergic rhinitis ("hay fever") and 9 percent of people without asthma or allergies, who develop asthmatic symptoms only when they exercise.

The condition can affect males and females of all ages, races and levels of fitness. Various studies have found that 3 to 11 percent of elite athletes have exercise-induced asthma. For example, tests among 597 members of the 1984 United States Olympic Team showed that 67 of them, or 11 percent, had asthma or exercise-induced asthma; still, these 67 athletes brought home 41 medals. They were able to compete so successfully because they were in tiptop physical condition and because their condition was effectively treated with airway-opening drugs before competition. Missed Diagnosis

Dr. Donald A. Mahler, a pulmonologist at Dartmouth-Hitchcock Medical Center in Lebanon, N.H., estimates that 12 to 15 percent of Americans are likely to develop one or more asthmatic symptoms either during vigorous activity or, more typically, within 15 minutes after exercising. These symptoms, which typically last 20 to 30 minutes, may include a feeling of tightness in the chest, shortness of breath, wheezing and coughing.

Those whose only noticeable symptom is a post-exercise cough often do not realize they have asthma, even though their ability to move air in and out of their lungs may be reduced by as much as 85 percent after exercise. Others in whom the condition goes undiagnosed do not know that their symptoms are abnormal and assume that everyone has trouble breathing after a vigorous workout.

Young children can also have unrecognized exercise-induced asthma. Instead of complaining about their breathing difficulties, they sometimes quietly retreat into sedentary activities after finding they cannot keep up with their peers.

Writing in the journal Medicine and Science in Sports and Exercise, Dr. Mahler urged a careful medical workup for anyone with exercise-related symptoms that resemble asthma, including just a cough. Like ordinary asthma, under certain conditions exercise-induced asthma can become life-threatening. The journal Emergency Medicine says exercise-induced asthma should be suspected in any child who avoids physical activity for no apparent reason. High and Low Risks

Although the precise causes of exercise-induced asthma are not known, experts believe the symptoms are induced by the drying and cooling effects of air that moves rapidly in and out of the respiratory tract. Symptoms are usually worse during outdoor exercise in winter and in activities that create a wind effect, like running, cycling and skating. Mouth breathing, which is necessary during a vigorous aerobic workout, reduces warming of air in the nasal passages.

Vigorous distance running is the common activity most likely to set off asthmatic symptoms. Cycling, skiing (both downhill and cross-country), speed skating, Rollerblading, sledding and water-skiing may cause problems for many people. Short bouts (5 to 10 minutes) of very intense exercise can also be troublesome, although shorter track and field events are often all right.

Stop-and-go activities like football, baseball and even tennis are much less likely to produce asthmatic symptoms. Workouts on indoor equipment like a stationary bike, treadmill or ski machine are usually easier to handle than the same activities done outdoors. Least likely to cause trouble are water-based activities like swimming and aquatic aerobics in an indoor pool, because the inhaled air is warm and saturated with water. Managing Problem

Medication and measures to reduce exposure to triggering factors can enable almost any person with exercise-induced asthma to achieve and maintain physical fitness and participate in sports. In fact, achieving fitness is one way to reduce the likelihood that asthmatic symptoms will interfere with activities.

In addition to cold air, another trigger factor is exposure to allergy triggers like air pollution, cigarette smoke, dust and high pollen counts. When smog blankets your area or the pollen count is high, it may be best to exercise indoors. When the air is chilly, scarf over the nose and mouth or a face mask can help warm incoming air and cut heat loss from lungs. Warmup

Before a vigorous workout or sports competition, Dr. Mahler and other experts strongly recommend a 15-minute exercise warmup followed by a 15-minute rest period; afterward, about half of people prone to exercise-induced asthma are less likely to be affected by the very same exercise for about two hours. Another approach is to "run through" symptoms that start 5 or 10 minutes into the exercise; they will often subside. Medication

Bronchodilating drugs are often essential to the comfort and safety of those with exercise-induced asthma. Treatment must be individualized; what works for one person may not work for another. The first line of therapy is an aerosol containing a beta-adrenergic agonist: albuterol, bitolterol, metaproterenol, pirbuterol or terbutaline. The inhalant should always be used just before and if necessary during the activity, if breathing problems develop. Those who need inhalers should always have them on hand during exercise.

If this treatment is ineffective, it can be combined with another inhaled drug, cromolyn sodium. Used one to 20 minutes before exercise, Dr. Mahler said, it can inhibit constriction of airways. Other possible treatments are theophylline, antihistamines, inhaled steroids and cough suppressants. But he warned against over-the-counter drugs that contain epinephrine or ephedrine, which can overstimulate the heart of someone with exercise-induced asthma.